corona set physics limitation - lua

Question

How can I make my game character's physic is limited only to 'tilt' left and right a bit? Here's how I declared my character
collector = display.newImage ("ms_throw.png")
collector.x = 10
collector.y = 10
physics.addBody(collector, {friction = 1.0, bounce = 0.6})
ms_throw.png is an image of a man standing... so basically collector will move left to right (using accelerometer) and I need the actor to only tilt a bit when he's moving.. means I don't want it to turn upside down when I tilt the phone.. How do I achieve this?

Answer 1

The trick is to tweak the coordinatey of applyForce(forcex,forcey,coordinatex,coordinatey).
If there is significant friction, the object will tilt.
To limit the tilt angle, use a box to cage it.
local physics = require("physics")
physics.start()
physics.setGravity(0,10)
centerx = display.viewableContentWidth/2+(display.contentWidth-display.viewableContentWidth)/2
centery = display.viewableContentHeight/2+(display.contentHeight-display.viewableContentHeight)/2
borderx = (display.contentWidth-display.viewableContentWidth)/2
bordery = (display.contentHeight-display.viewableContentHeight)/2
local w = display.viewableContentWidth/2
local h = 100/2
local allowanceHeight = 15
local collectorLimiter = {}
--cannot do in createScene because need to do together with physics
local ix,iy = centerx,bordery+display.viewableContentHeight-60
collectorLimiter[1] = display.newRect(0,0,display.viewableContentWidth,4)
collectorLimiter[1].x,collectorLimiter[1].y = ix,iy-h-allowanceHeight
collectorLimiter[2] = display.newRect(0,0,display.viewableContentWidth,4)
collectorLimiter[2].x,collectorLimiter[2].y = ix,iy+h
collectorLimiter[3] = display.newRect(0,0,4,h*2+allowanceHeight)
collectorLimiter[3].x,collectorLimiter[3].y = ix-w,iy
collectorLimiter[4] = display.newRect(0,0,4,h*2+allowanceHeight)
collectorLimiter[4].x,collectorLimiter[4].y = ix+w,iy
for i = 1,#collectorLimiter do
--collectorLimiter[i].isVisible = false
end
physics.addBody(collectorLimiter[1],"static", {friction = 0.3,bounce = 0, filter = {categoryBits = 4,maskBits = 6} })
physics.addBody(collectorLimiter[2],"static", {friction = 0.3,bounce = 0, filter = {categoryBits = 4,maskBits = 6} })
physics.addBody(collectorLimiter[3],"static", {friction = 0.3,bounce = 0, filter = {categoryBits = 4,maskBits = 6} })
physics.addBody(collectorLimiter[4],"static", {friction = 0.3,bounce = 0, filter = {categoryBits = 4,maskBits = 6} })
local collector = display.newRect(0,0,80,100)
collector.x,collector.y = centerx,centery+480
physics.addBody(collector, {friction = 0.3, density = 0.2, bounce = 0, filter = {categoryBits = 2}} )
local function OnTouch(event)
-- Move our collector based on the accelerator values
if event.phase == "began" then
collector.ix,collector.iy = event.x,event.y
elseif event.phase == "moved" then
if collector.ix and collector.iy then
local dx = (event.x-collector.ix)*0.4
collector:applyForce(dx,0,collector.x,collector.y-10)
collector.ix,collector.iy = collector.x,collector.y
end
elseif event.phase == "ended" or event.phase == "cancelled" then
collector.ix,collector.iy = nil,nil
end
end
Runtime:addEventListener("touch",OnTouch)